net: dsa: microchip: monitor potential faults in half-duplex mode

The errata DS80000754 recommends monitoring potential faults in
half-duplex mode for the KSZ9477 family.

half-duplex is not very common so I just added a critical message
when the fault conditions are detected. The switch can be expected
to be unable to communicate anymore in these states and a software
reset of the switch would be required which I did not implement.

Fixes: b987e98e50ab ("dsa: add DSA switch driver for Microchip KSZ9477")
Signed-off-by: Enguerrand de Ribaucourt <enguerrand.de-ribaucourt@savoirfairelinux.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 51 insertions, 0 deletions

diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
index cbaca4140cda..425e20daf1e9 100644
--- a/drivers/net/dsa/microchip/ksz9477.c
+++ b/drivers/net/dsa/microchip/ksz9477.c
@@ -427,6 +427,57 @@ void ksz9477_freeze_mib(struct ksz_device *dev, int port, bool freeze)
 	mutex_unlock(&p->mib.cnt_mutex);
 }
 
+int ksz9477_errata_monitor(struct ksz_device *dev, int port,
+			   u64 tx_late_col)
+{
+	u32 pmavbc;
+	u8 status;
+	u16 pqm;
+	int ret;
+
+	ret = ksz_pread8(dev, port, REG_PORT_STATUS_0, &status);
+	if (ret)
+		return ret;
+	if (!(FIELD_GET(PORT_INTF_SPEED_MASK, status) == PORT_INTF_SPEED_NONE) &&
+	    !(status & PORT_INTF_FULL_DUPLEX)) {
+		/* Errata DS80000754 recommends monitoring potential faults in
+		 * half-duplex mode. The switch might not be able to communicate anymore
+		 * in these states.
+		 * If you see this message, please read the errata-sheet for more information:
+		 * https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9477S-Errata-DS80000754.pdf
+		 * To workaround this issue, half-duplex mode should be avoided.
+		 * A software reset could be implemented to recover from this state.
+		 */
+		dev_warn_once(dev->dev,
+			      "Half-duplex detected on port %d, transmission halt may occur\n",
+			      port);
+		if (tx_late_col != 0) {
+			/* Transmission halt with late collisions */
+			dev_crit_once(dev->dev,
+				      "TX late collisions detected, transmission may be halted on port %d\n",
+				      port);
+		}
+		ret = ksz_read8(dev, REG_SW_LUE_CTRL_0, &status);
+		if (ret)
+			return ret;
+		if (status & SW_VLAN_ENABLE) {
+			ret = ksz_pread16(dev, port, REG_PORT_QM_TX_CNT_0__4, &pqm);
+			if (ret)
+				return ret;
+			ret = ksz_read32(dev, REG_PMAVBC, &pmavbc);
+			if (ret)
+				return ret;
+			if ((FIELD_GET(PMAVBC_MASK, pmavbc) <= PMAVBC_MIN) ||
+			    (FIELD_GET(PORT_QM_TX_CNT_M, pqm) >= PORT_QM_TX_CNT_MAX)) {
+				/* Transmission halt with Half-Duplex and VLAN */
+				dev_crit_once(dev->dev,
+					      "resources out of limits, transmission may be halted\n");
+			}
+		}
+	}
+	return ret;
+}
+
 void ksz9477_port_init_cnt(struct ksz_device *dev, int port)
 {
 	struct ksz_port_mib *mib = &dev->ports[port].mib;